用java实现上传下载功能

package  bean.sendmail;

import  java.io.*;  
import  javax.servlet.http.HttpServletRequest;  
import  javax.servlet.ServletInputStream;  
import  javax.servlet.ServletException;  

public  class  upload{
    private  static  String  newline  =  "\n";
    private  String  uploadDirectory  =  ".";
    private  String  ContentType  =  "";
    private  String  CharacterEncoding  =  "";
    private  String  strFileName  =  "";
    private  long  iFileSize  =  0;
          
    private  String  getFileName(String  s){
          int  i  =  s.lastIndexOf("\\");
          if(i  <  0  ||  i  >=  s.length()  -  1){
                i  =  s.lastIndexOf("/");
                if(i  <  0  ||  i  >=  s.length()  -  1)
                      return  s;
          }
          strFileName  =  s.substring(i  +  1);
          return  s.substring(i  +  1);
    }
    
    public  String  getUploadFileName(){
          return  strFileName;
    }
    
    public  long  getFileSize(){
          return  iFileSize;
    }
    
    public  void  setUploadDirectory(String  s){
          uploadDirectory  =  s;
    }

    public  void  setContentType(String  s){
          ContentType  =  s;
          int  j;
          if((j  =  ContentType.indexOf("boundary="))  !=  -1){
                ContentType  =  ContentType.substring(j  +  9);
                ContentType  =  "--"  +  ContentType;
          }
    }
    
    public  void  setCharacterEncoding(String  s){
          CharacterEncoding  =  s;
    }

    public  void  uploadFile(  HttpServletRequest  req)  throws  ServletException,  IOException{
          setCharacterEncoding(req.getCharacterEncoding());
          setContentType(req.getContentType());
          uploadFile(req.getInputStream());
    }  

    public  void  uploadFile(  ServletInputStream  servletinputstream)  throws  ServletException,  IOException{
          String  s5  =  null;
          String  filename  =  null;
          byte  Linebyte[]  =  new  byte[4096];
          byte  outLinebyte[]  =  new  byte[4096];
          int  ai[]  =  new  int[1];
          int  ai1[]  =  new  int[1];
          String  line;
          //得到文件名
          while((line  =  readLine(Linebyte,  ai,  servletinputstream,  CharacterEncoding))  !=  null){
                int  i  =  line.indexOf("filename=");
                if(i  >=  0){
                      line  =  line.substring(i  +  10);
                      if((i  =  line.indexOf("\""))  >  0)
                            line  =  line.substring(0,  i);
                      break;
                }
          }
          
          filename  =  line;
          
          if(filename  !=  null  &&  !filename.equals("\"")){
                filename  =  getFileName(filename);
                
                String  sContentType  =  readLine(Linebyte,  ai,  servletinputstream,  CharacterEncoding);
                if(sContentType.indexOf("Content-Type")  >=  0)
                      readLine(Linebyte,  ai,  servletinputstream,  CharacterEncoding);
                      
                //File(String  parent,  String  child)
                //Creates  a  new  File  instance  from  a  parent  pathname  string
                //and  a  child  pathname  string.
                
                File  file  =  new  File(uploadDirectory,  filename);
                
                //FileOutputStream(File  file)
                //Creates  a  file  output  stream  to  write  to  the  file  represented
                //by  the  specified  File  object.
                
                FileOutputStream  fileoutputstream  =  new  FileOutputStream(file);
                
                while((sContentType  =  readLine(Linebyte,  ai,  servletinputstream,  CharacterEncoding))  !=  null){
                      if(sContentType.indexOf(ContentType)  ==  0  &&  Linebyte[0]  ==  45)
                            break;
                      if(s5  !=  null){
                      
                            //write(byte[]  b,  int  off,  int  len)
                            //Writes  len  bytes  from  the  specified  byte  array  starting
                            //at  offset  off  to  this  file  output  stream.
                      
                            fileoutputstream.write(outLinebyte,  0,  ai1[0]);
                            fileoutputstream.flush();
                      }
                      s5  =  readLine(outLinebyte,  ai1,  servletinputstream,  CharacterEncoding);
                      if(s5  ==  null  ||  s5.indexOf(ContentType)  ==  0  &&  outLinebyte[0]  ==  45)
                            break;
                      fileoutputstream.write(Linebyte,  0,  ai[0]);
                      fileoutputstream.flush();
                }
          
                byte  byte0;
                if(newline.length()  ==  1)
                      byte0  =  2;
                else
                      byte0  =  1;
                if(s5  !=  null  &&  outLinebyte[0]  !=  45  &&  ai1[0]  >  newline.length()  *  byte0)
                      fileoutputstream.write(outLinebyte,  0,  ai1[0]  -  newline.length()  *  byte0);
                if(sContentType  !=  null  &&  Linebyte[0]  !=  45  &&  ai[0]  >  newline.length()  *  byte0)
                      fileoutputstream.write(Linebyte,  0,  ai[0]  -  newline.length()  *  byte0);
                
                iFileSize  =  ffile.length();
                fileoutputstream.close();
          }
    }
    
    private  String  readLine(byte  Linebyte[],  int  ai[],  ServletInputStream  servletinputstream,  String  CharacterEncoding){
          try{
                //readLine(byte[]  buffer,  int  offset,  int  length)
                //Reads  a  line  from  the  POST  data.
                ai[0]  =  servletinputstream.readLine(Linebyte,  0,  Linebyte.length);
                if(ai[0]  ==  -1)
                      return  null;
          }catch(IOException  _ex){
                return  null;
          }
          
          try{
                if(CharacterEncoding  ==  null){
                      //用缺省的编码方式把给定的byte数组转换为字符串
                      //String(byte[]  bytes,  int  offset,  int  length)
                      return  new  String(Linebyte,  0,  ai[0]);
                }else{
                      //用给定的编码方式把给定的byte数组转换为字符串
                      //String(byte[]  bytes,  int  offset,  int  length,  String  enc)
                      return  new  String(Linebyte,  0,  ai[0],  CharacterEncoding);
                }
          }catch(Exception  _ex){
                return  null;
          }
    }  
/*  
public  int  readLine(byte[]  buffer,  
int  offset,  
int  length)  throws  java.io.IOException  
从POST来的数据中读一行  
参数:  
buffer  -  buffer  to  hold  the  line  data  
offset  -  offset  into  the  buffer  to  start  
length  -  maximum  number  of  bytes  to  read.  
Returns:  
number  of  bytes  read  or  -1  on  the  end  of  line.  
*/  
}